Formal events can either be black tie or white tie, and each comes with different guidelines. As a general rule of thumb, most events are black tie unless the invitation specifically states that white tie is required.
For black tie formal events, men should wear a tuxedo with a cummerbund and matching bow tie. Women can wear either a floor-length gown or cocktail-length dress. All accessories should be upscale and formal.
White tie events are more formal than black tie events. White tie calls for a black tuxedo with a white tie and cummerbund for men and a floor-length evening gown for women. White tie formal events are not the place to show creativity with extreme color choices or short dresses. Women can opt to wear white gloves to white tie events.
For any level formal event, it's always important to look your best. Clothes should be wrinkle and stain free. Hair should be neatly groomed, and women can opt for a dramatic up-do. Accessories such as shoes and jewelry don't have to cost a lot, but they should look as if they do. When in doubt, it's best for women to go with a floor-length gown in a conservative style.